Electronic grade acetic acid is an important solvent and indispensable electronic chemical in the electronic industry. Some particulates, metal ions, unreacted raw materials, and intermediate products or by-products will be in the acetic acid because of the raw materials and equipments used during production, transportation and storage. The existence of these impurities, in particular metal ions, can lead to Oxidation Induced Stacking Faults (OISF) so that the PN Junction Leakage Current increases, Breakdown occurs, and the life of current carrier shortens. Even a small quantity of metal ions or particulates can destroy the whole circuit when the line width of the integrated circuit is thin. Therefore the purity of electronic chemicals is critical to ensure the development of a super large-scale integrated circuit. Therefore, the purity of electronic chemicals must meet the demands of nanometer-grade IC.
The key to the production of liquid Ultra-clean and High-purity Reagents (or Process Chemicals) such as acetic acid is ensuring the content of impurities (such as metal ions etc.) and granularity is in conformity with the standard of requirement. Presently, the main producing methods include ionized sub-boiling distillation, azeotropic distillation, (multistage) rectification, and chemical treatment, etc. However, there isn't a satisfactory method for producing electronic grade acetic acid.
Multistage rectification, such as the two-stage rectification method and equipment disclosed in Chinese patent No.CN1285560C, to produce acetic acid in conformity with the SEMI-C7 standard is the most commonly used method for producing of ultra-clean and high purity acetic acid. The multistage rectification results in continuous production over a long period of time, but requires heavy energy consumption and high risk.
Chinese patent No.CN100372586C disclosed a method and equipment for producing ultra-clean and high-purity acid. The method and equipment is composed of a barbed rectification tower and a filled tower in series to produce electronic acid such as hydrochloric acid and acetic acid. This method improves the conventional method. However, the internal structure of the required equipment is complicated.